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Velocity Segregation and Systematic Biases in Velocity Dispersion Estimates with the SPT-GMOS Spectroscopic Survey

Matthew BaylissKavli Institute for Astrophysics & Space Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA;[email protected]Kyle ZengoDepartment of Physics and Astronomy, Colby College, 5100 Mayflower Hill Drive, Waterville, ME 04901, USAJ. RuelDepartment of Physics, Harvard University, 17 Oxford Street, Cambridge, MA 02138, USAB. A. BensonDepartment of Astronomy and Astrophysics, University of Chicago, Chicago, IL, USA 60637, USAL. E. BleemArgonne National Laboratory, Argonne, IL, USA 60439, USAS. BocquetArgonne National Laboratory, Argonne, IL, USA 60439, USAEsra BulbulKavli Institute for Astrophysics & Space Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA;[email protected]M. BrodwinDepartment of Physics and Astronomy, University of Missouri, 5110 Rockhill Road, Kansas City, MO 64110, USAR. CapassoExcellence Cluster Universe, Boltzmannstr. 2, D-85748 Garching, GermanyI-Non ChiuAcademia Sinica Institute of Astronomy and Astrophysics (ASIAA) 11F of AS/NTU Astronomy-Mathematics Building, No.1, Sec. 4, Roosevelt Road,Taipei 10617, TaiwanM. McDonaldKavli Institute for Astrophysics & Space Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA;[email protected]David RapettiCenter for Astrophysics and Space Astronomy, Department of Astrophysical and Planetary Science, University of Colorado, Boulder, C0 80309, USAAlex SaroExcellence Cluster Universe, Boltzmannstr. 2, D-85748 Garching, GermanyB. StalderInstitute for Astronomy, the University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USAA. A. StarkHarvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USAV. StrazzulloExcellence Cluster Universe, Boltzmannstr. 2, D-85748 Garching, GermanyC. W. StubbsDepartment of Physics, Harvard University, 17 Oxford Street, Cambridge, MA 02138, USAA. ZentenoCerro Tololo Inter-American Observatory, Casilla 603, La Serena, Chile

2017en

ABI

Annotatsiya

Abstract The velocity distribution of galaxies in clusters is not universal; rather, galaxies are segregated according to their spectral type and relative luminosity. We examine the velocity distributions of different populations of galaxies within 89 Sunyaev Zel’dovich (SZ) selected galaxy clusters spanning . Our sample is primarily draw from the SPT-GMOS spectroscopic survey, supplemented by additional published spectroscopy, resulting in a final spectroscopic sample of 4148 galaxy spectra—2868 cluster members. The velocity dispersion of star-forming cluster galaxies is 17 ± 4% greater than that of passive cluster galaxies, and the velocity dispersion of bright ( ) cluster galaxies is 11 ± 4% lower than the velocity dispersion of our total member population. We find good agreement with simulations regarding the shape of the relationship between the measured velocity dispersion and the fraction of passive versus star-forming galaxies used to measure it, but we find a small offset between this relationship as measured in data and simulations, which suggests that our dispersions are systematically low by as much as 3% relative to simulations. We argue that this offset could be interpreted as a measurement of the effective velocity bias that describes the ratio of our observed velocity dispersions and the intrinsic velocity dispersion of dark matter particles in a published simulation result. Measuring velocity bias in this way suggests that large spectroscopic surveys can improve dispersion-based mass-observable scaling relations for cosmology even in the face of velocity biases, by quantifying and ultimately calibrating them out.

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DOI: 10.3847/1538-4357/aa607c

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